The present invention relates to a system for injecting a fluid, such as water or a water solution, into an internal combustion engine and, more specifically, to a fluid injection system and method for injecting fluid into an internal combustion engine in which the injection rate is proportional to engine speed and engine load.
Various cooling fluids, such as water and water in solution with other substances, such as methanol or alcohol, have been commonly injected into hydrocarbon engines, both of the spark-ignition and compression-ignition type, to provide improved engine operation. These improvements are possible since, during the compression stroke of the engine, the water droplets evaporate and thus absorb heat and prevent pre-ignition. On the power stroke the gasoline is burned and the remaining water is turned to steam which absorbs more heat and helps prevent detonation. Also, as the water turns to steam, it undergoes considerable expansion which produces significant additional power. Further, as a result of the above, combustion occurs at lower temperatures and is more even, and the pistons and valves enjoy a longer life. Further, the presence of water also creates a "steam cleaning" process that tends to remove carbon and other deposits from the combustion chamber, as well as prevent the formation of additional deposits.
Various types of prior devices have been used to introduce cooling fluids into internal combustion engines. These devices have included nozzle-type injectors in which the fluid is pumped directly into the engine and intake air humidifiers in which air is passed through a volume of water before being introduced into the engine. However, since the injection of a relatively low volume of fluid is desired when compared to the volume of fuel introduced into the engine, it is difficult, if not impossible, to meter the fluid with the precision needed to insure optimum performance when it is pumped directly into the engine. Also, if humidified air is used, there is a reduction in power and fuel economy, since the humidified air is less dense that dry air with water droplets. Also, the use of humidified air does not permit the cooling effect caused by the evaporation of the water droplets.
These prior devices suffer from additional problems, since they are usually operated solely in response to engine speed, or by the exhaust gases from the engine, either directly or as modified by the engine intake manifold pressure. Although these techniques result in a fluid injection rate that may be adequate under certain engine operating conditions, such as a constant-speed cruise condition, the injection rate during other engine operating conditions, such as acceleration and deceleration, may be too little or too much. When the fluid injection rate is insufficient, the beneficial effects of the cooling fluid are, of course, not obtained. Conversely, when the injection rate is too high, the surplus fluid within the combustion chamber tends to quench the combustion process and, of course, diminish engine performance.